First light from. Gagan Mohanty

Transcription

1 First light from Gagan Mohanty March 17-23, 2019

2 Flavor physics: why? E~m Δm.Δt ~ 1 ~ TeV Ø Provides us a unique probe to unravel deeper mysteries of the universe with intense sources and highly sensitive detectors q Main players at energy and intensity frontiers: 1

3 Some of the grand questions for FP q Are there any new CP violating phases? ècp violation (CPV) in B and D decays q Any right-handed current from new physics? èphoton polarization in radiative decays q Are there any imprints of new physics beyond the SM in flavor changing neutral current transitions? èelectroweak penguin decays e.g. b sll q Are there any signature of charged Higgs boson? Or, leptoquark? ètree-level B decays to τν or D (*) τν final state q Neutrino oscillation being firmly established, what are the implications for lepton flavor violation in the charged lepton sector? èlepton flavor violating (LFV) tau decays q Understanding exotic QCD states? Tetraquark, pentaquark, hybrid? q Can we chase down dark matter from bottom? Hidden dark sector? 2

4 q Will address a broad range of topics: CKM metrology A new player on the field G. Caria Tree-level decays B D (*) lν arxiv: LFV tau decays NP probe in EW penguin M. Prim 3

5 SuperKEKB: New intensity frontier machine 50nm q Targets to deliver e+e collisions at a peak luminosity of cm 2s 1 è 40 times that of KEKB: ² Increase beam currents twice ² Reduce beam size by 20 times SuperKEKB KEKB 100µ m 1µm 5mm 4 GeV 7 GeV Ø First new particle collider after LHC! 4

6 How far have we gone? q Phase 2 (2018): beam commissioning (establish nano-beam scheme, reach the KEKB luminosity, and measure beam backgrounds) as well as do some physics with partial vertex detector è ~500 pb 1 q Phase 3 (2019 onward): physics run with the vertex detector q Phase-2 record was σ y* = 400nm with only ~15mA beam currents q Continue with β y* = 3mm for the early phase 3 (expect collisions by end of this week) Phase-2 record q Gradually increase beam currents and reduce the beam size 5

7 Belle II: A 21 st century HEP experiment q Designed to operate with a performance similar to or better than Belle, but in a harsh beam background condition EM Calorimeter (ECL): CsI(Tl) crystals, waveform sampling readout K L and muon detector: Resistive plate counter (barrel outer), plastic scintillator + WLS fiber + SiPM (endcap and inner two barrel layers) electrons (7 GeV) Beryllium beam pipe (2 cm diameter) Vertex Detector (VXD): 2-layer pixel (PXD) + 4-layer strip (SVD) Central Drift Chamber (CDC): He(50%)+C2H6(50%), small cells, long lever arm, fast electronics Particle identification: Time-of-Propagation counter (barrel) Prox. focusing Aerogel RICH (forward) positrons (4 GeV) 6

8 Tracking system is working fine! q Charged tracks reconstructed using info mostly from the CDC are available since the beginning of collisions q Mass resolutions of known particles in data in agreement with simulations (B field measured well and sub-detectors also aligned) 7

9 Neutral construction: Belle II strength q All set to probe the dark sector: 8

10 Particle identification: A key element q Kaon track is kinematically tagged by the charge of π s arising from the D* decays A TOP event q Check consistency of hit pattern (x vs. t) of Cherenkov photons Ø PID capability with early calibration & alignment 9

11 Rediscovery of B mesons Spherical (R 2 ~ 0) Jetlike (R 2 ~ 1) q Event topology tells us that we are seeing spherical BB events q Further proof came from the plot of the beam-energy constrained mass 10

12 VXD: Another key element is now ready One half of VXD Partial VXD of Phase 2 L6 L5 L4 L3 L2 L1 q Large improvement in vertex resolution q PXD: L1+1/6 of L2 (rest will be added in 2020) VXD installed to Belle II (Nov 2018) In global cosmic since Jan

13 Early physics harvesting from Phase 3 q Integrated luminosity will depend on machine and detector performance q Nevertheless, we expect around 10 fb 1 by Summer 2019 that would be used to study an array of topics Low multiplicity: Ø Dark photon, ALP (1-2 fb 1 ) Ø Magnetic monopole (0.5 fb 1 ) Tau: Ø τ lα, ωhν, ωhπ 0 ν (1 fb 1 ) Ø Lifetime (2 fb 1 ) Charm: Ø D lifetime (2 fb 1 ) Ø Doubly Cabibbo suppressed D 0 K + π, K + π π 0 (10 fb 1 ) Semileptonic B: Ø B D (*) lν untagged ( fb 1 ) Ø B π/ρlν untagged (2-10 fb 1 ) Charmless B (no time dependent): Ø B Kπ (10 fb 1 ) Ø B φk (10 fb 1 ) Charmed B: Ø B D (*) h CF decays (1 fb 1 ) Ø B D (*) K, D (*) π 0 (10-20 fb 1 ) EW penguins: Ø B K * γ (2 fb 1 ) Ø B X S γ (2-10 fb 1 ) Time-dependent CPV: Ø B lifetime (2-10 fb 1 ) Ø Mixing in B Dh, Dlν (2-10 fb 1 ) Ø sin 2φ 1 in B J/ψK S and related modes (10+ fb 1 ) 12

14 Closing words q Belle II will probe new physics at the intensity frontier ècomplementary to high p T programs of ATLAS and CMS experiments at the LHC q As for LHCb, there is healthy competition and complementarity q Marathon (physics run) has just begun in the super factory mode è need high-efficiency data taking as well as extensive running of SuperKEKB q First results expected by 13

15 q q q q >800 members 104 institutions 26 countries 4 continents! 14

16 Belle II vs. LHCb Ø Great for neutral and missing energy modes Ø Inclusive measurement: OK Ø Excellent flavor tagging and K S reconstruction 15

17 Comparison: KEKB vs. SuperKEKB 16

18 Global Belle II schedule 17

19 Beam background commissioning arxiv: Touschek Coulomb scattering Bremsstrahlung Bhabha scattering Beam-gas + Synchrotron radiation Two-photon Touschek (intra-bunch scattering) 18